Security sources warned that the terrorists were likely to change tactics again. The overnight switch from using huge lorry bombs in London to smaller, indiscriminately placed Semtex bombs in Manchester was evidence of a new more flexible strategy. One senior source said: 'If we ask people to look for lorries carrying bombs, then we find that within a couple of days they are planting them in shop doorways or left in bins.'
The Government yesterday refused to give assurances that it would pay the insurance bill for terrorist attacks in Britain - as it does in Northern Ireland - despite pleas from the CBI. Insurers have insisted that they will not provide cover because the risks are too high.
The pre-Christmas period is traditionally a time of heightened activity and last year saw a series of incendiary bombs planted in shopping areas.
Early yesterday morning, a soldier on guard duty at an ammunition compound in Catterick army camp in North Yorkshire fired five shots at two or three men, believed to be armed, entering a restricted area.
Police and the Army said it was impossible to establish whether the intruders were IRA members or poachers, who are common in the area. A police spokesman said that if the intruders were poachers they should contact the police, who would treat them sympathetically.
The shooting led to an alert and precautions around the camp were tightened as police were called in to search the area.
A number of military bases have been attacked in the current campaign and a return to such targets would be a typical move. Catterick, which houses 20,000 troops who do regular tours in Northern Ireland, is a recognised target and soldiers are on a permanent state of alert.
In Manchester, the city centre was reopened after the injuries and destruction caused by Thursday's bombs. Apart from damaged buildings and small areas around the bomb sites, the public was able to return to shops and businesses. Only one of those injured was detained in hospital overnight.
The IRA statement issued in Dublin said: 'Active service units of the IRA carried out this week's military operations aimed at government and commercial targets in London's West End and Manchester.
'In both cases adequate and clear warnings were given. Until the British government recognises Ireland's right to national self- determination, attacks such as these will continue.'
Usdaw, the shopworkers' union, yesterday called upon the Government and employers to introduce better training and emergency procedures for spotting suspect packages and dealing with bomb alerts and evacuations.
Michael Heseltine, President of the Board of Trade, said that he would be having further discussions with insurers. The CBI warned that business could be 'devastated' unless the Government was prepared to take responsibility. Mike Jones, chief executive of the Association of British Insurers, said: 'It is not just a matter of premiums. We are saying that the insurance industry worldwide cannot and will not underwrite this risk.'
After 1 January, insurance cover on terrorist-related payouts for commercial policies will be cut to a ceiling of pounds 100,000.